Long read - sorry and thanks again for entertaining my crazy ideas..
I like the Idea of moving the weight outside so It can become adjustable. Since this bike made of leftovers is for dirt fun I assume a stator is completely unnecessary allowing a custom primary cover (magneto timing cover)
I am always reading conflicting information on the need for a flywheel in racing
My limited experience in racing revealed to me that the lightest possible rotating assembly was the fastest around and down the track
In 99 I did my best to build (on a minimum wage budget) a drag racing car out of my daily driver 1985 VW Golf 8v
Saving the specifics the car made 176hp at the wheels on a Mustang brand brake dyno (2 rollers). This dyno was at the shop where I worked so I was always checking every modification.
Just for comparison a friendly shop let me check my car on their Dynajet inerta dyno 1 roller as we were having the conversation that the Mustang dynos are consistently low compared to Dynajet stuff - Sure enough my car with no modifications since it's 176 pull made 208 on his dyno. All the correction and calibration factors aside amongst the car guys it was said the Mustang read on average 20-25% lower for some reason.
On the Mustang dyno my car gained no power when I swapped the 28lb flywheel for the 7lb unit I made on a brake lathe.
At the race track (1/4 mile drag strip) I gained a consistent half-second in my overall ET. Not just one run but from then on. The car felt like I picked up 15+ horsepower - the original seat of the pants dyno. Fastest run 13.1..a proud skinny broke kid was I.
Later in life I applied the same flywheel tactic to my over budget 350 powered 67 Firebird and no change. From the heavy 30lb flywheel to an alloy 10lb unit showed no faster at the drag strip but the seat of the pants pulling power felt amazing. The car was hard to handle overall since it was making 4x more power than the VW and weighed 3000lbs with me in it and the fuel cell full at 5 gal.
In my road racing try I was running a CB200 around the Sonoma track here in California. I shaved 8 seconds off my lap times that day by removing the stator flywheel in the parking lot. The bike pulled so much harder without that extra mass to spin up and that seemed consistent with the other GP200 riders.
In my sand drag racing experience the guys with flywheels were the spectators. None of us ran flywheels on our modern Methanol/Nitro powered single cyl stuff and the big boys ran no flywheels also.
Sprint cars- no flywheels
Top fuel drag racing - No flywheels, but there is a clutch pack
Speedway motorcycles - heavy crank/flywheels - Needed? likely yes..the ability for the heavy mass to store energy is useful..I raced a 4 valve jawa then a 4 valve Weslake and I cant imagine not having that power stored up and already spinning when trying to turn with the rear wheel
Road Racing?..I don't believe a heavy flywheel is useful (subjective I know)..then again maybe it is completely track and driver/rider dependent. Think autocross - building an autocross car requires to assemble lightest possible ride (within budget) with the quickest engine. I have always understood a light flywheel is similar to a light vehicle -less mass to move.
Having mush less rotating mass should actually free up power as it takes less energy to make it spin, it should, but I did not see it on my 1 dyno test back in the ol days on my VW.
Technically when the target RPM is reached then there is much less power needed to keep a heavy spinning flywheel there..maybe land speed racing?...generators?....Pumps?
I am a firm believer that I can go faster without one, but will it possible on the Triumph engine I have slated for this dirt bike?
When it comes to hill-climbing and off road wheelie machines I cant see a reason for one as it is also a detriment to the engine in such an abusive environment. I expect to see low rpm grunt to the common loss of traction off a jump, high rpm spin up and maybe damaging flywheel flex
Not to mention it can shave 20+ lbs from the engine overall
..but having said all that I really like the idea of 76 degrees and a flywheel mounted outside if possible...